A Vacuum of the Imagination — Angadh Nanjangud

A Vacuum of the Imagination

Why Space Rockets Could Have Flown Centuries Earlier

Completion: 60%

4042 words

Essay first planted: June 30, 2026 • Last updated: July 15, 2026

space, technology, history-of-technology

Introduction

I have long suspected space rockets could have been invented earlier than Goddard’s 1926 flight — but why did we wait until then to see them? This essay sits within a family of other explorations into understanding why inventions appear when they do. The general consensus is that “most useful technologies tend to be invented quite quickly once they are possible”, but this feels untrue for rockets.

For the purpose of this writeup, I’ll define a space rocket as one based on its technical intention, not flight success; Goddard’s was to reach the Moon, stated in his 1919 paper “A Method of Reaching Extreme Altitudes”. That intention, not success, is a necessary and sufficient condition to define a space rocket. It should be acceptable even today: more upstart space-rocket companies are yet to successfully achieve orbit, but their intent is what defines them. Goddard’s first rocket flew to an altitude of 12.5 metres and the highest altitude he achieved was roughly 2.7 km; this provides some justification for also considering amateur rocketry in this essay. Hobbyist rocketry today is a signal of intent from students wanting to work in the space industry, and a somewhat serious hobby for others generally interested in space exploration. So, I also lean on this group in developing this essay to answer when rockets could first have appeared and why they didn’t happen earlier.

It is worth noting that liquid space rockets emerging before solid ones is historically unusual; a harder, higher-performing technology doesn’t often mature before a simpler one. But this invention sequence might actually have resulted in space progress happening more slowly than it should have. Here, I make the case that the critical innovation of both rockets — their propellant — could have happened several centuries earlier!

It is also useful to have some preliminary knowledge of rocket propellants; propellants are principally a mixture of a fuel and its oxidiser. Liquid propellants that commonly power space rockets control the mixing of the two in the combustion chamber by storing them in separate tanks. When they enter the combustion chamber, they are either ignited using an external source or self-ignite on contact (a phenomenon called hypergolicity). SpaceX’s Falcon rockets have Merlin Engines that use liquid oxygen (LOX) to oxidise rocket-grade kerosene whereas Starship’s first stage (i.e., Super Heavy) has 33 Raptor engines burning liquid methane and LOX (also called methalox). Methalox behaves like a hypergolic pair but isn’t: Raptor pre-burns both fuel and oxidiser before they are allowed to mix in the main chamber as gases hot enough to ignite on mixing — thermal autoignition rather than the chemical self-ignition of true hypergols. Falcon’s Merlin engines inject a pyrophoric (triethylaluminium-triethylborane) to trigger combustion. Solid propellants are commonly used in missiles or as boosters to the main liquid-fuelled launch vehicle. Common solid rocket fuels are typically produced by casting: the fuel is melted or mixed as a fluid with oxidiser crystals suspended in it, then poured into the casing, where it solidifies as a single bonded grain.

So when was a space rocket possible?

A recent Claude-driven analysis concluded that Goddard’s liquid-fuelled rocket appears shortly after it was technically possible1 to produce LOX at an industrial scale. That Sputnik followed only 30 years later suggests spaceflight hinged on the LOX production constraint being lifted. But this doesn’t really answer “what other liquid oxidisers existed or could have been invented earlier?” The aforementioned list of 190 inventions also doesn’t contain purely solid-fuelled orbital-class vehicles that were eventually invented; this begs a similar analysis into solid propellant rockets: were they also bottlenecked? If neither of these turn out to be specific bottlenecks, then what other factors might have prevented the space rocket from taking flight earlier?

Solid propellant stagnates on black powder for a thousand years while refrigeration research delivers the idea of liquid fuels to Tsiolkovsky. The Cold War military research brings solids back into the picture. Open full size ↗

How much earlier could liquid propellants have been invented?

John D. Clark’s Ignition, a fun read on the history of liquid propellants, points to liquefaction — specifically, the ability to convert oxygen and hydrogen gas into liquid oxidiser and fuel respectively — being pivotal to enabling liquid-fuelled rockets. From his eponymous equation, Tsiolkovsky concluded that this liquid fuel-oxidiser combination is vastly superior to gunpowder, a millennium-old solid propellant for artillery —...